A. Field of the Invention
The device of the present invention generally relates to molded case circuit breakers and, more particularly, to electrical contacts used in such circuit breakers.
B. Description of the Prior Art
Circuit breakers and, more particularly, molded case circuit breakers are old and well known in the prior art. Examples of such devices are disclosed in U.S. Pat. Nos. 3,525,959; 3,614,865; 3,815,059; 3,863,042; 4,077,025; and 4,166,205. In general, prior art molded case circuit breakers have been provided with movable contact arrangements and operating mechanisms designed to provide protection for an electrical circuit or system against electrical faults, specifically, electrical overload conditions, low level short circuit or fault current conditions, and, in some cases, high level short circuit or fault current conditions. Prior art devices have utilized a trip mechanism for controlling the movement of an overcenter toggle mechanism to separate a pair of electrical contacts upon an overload condition or upon a short circuit or fault current condition. Such trip mechanisms have included a bimetal movable in response to an overload condition to rotate a trip bar, resulting in the movement of the over-center toggle mechanism to open a pair of electrical circuit breaker contacts. Such prior art devices have also utilized an armature movable in response to the flow of short circuit or fault current to similarly rotate the trip bar to cause the pair of contacts to separate. At least some prior art devices use blow-apart contacts to rapidly interrupt the flow of high level short circuit or fault currents.
While many prior art devices have provided adequate protection against fault conditions in an electrical circuit, a need exists for dimensionally small molded case circuit breakers capable of fast, effective and reliable operation and, more specifically, for a compact, movable under electrical contact capable of rapid movement away from an associated lower electrical contact during high level short circuit or fault current conditions, such movement being independent of and in advance of the sequencing of the operating mechanism of the circuit breaker through a trip operation.